It is known with tackers for the depth of penetration of the fastening element to be adjustable. With tackers known in the art (e.g. German Pat. No. 1,603,827), which are, however, more commonly driven with compressed air, adjusting of the depth of penetration of the fastening elements is effected by modifying the position of the bearing area, or discharge nozzle, of the discharge duct of the fastening elements. To do this the nozzle or duct mouthpiece is moved in the direction of movement of the fastening element, and thus in the direction of movement of the driving element acting upon the fastening element. This usually requires loosening, adjusting, and re-tightening the entire duct mouthpiece or a confining wall of the front area of the discharge duct. Providing for such an adjustment is relatively costly to manufacture. Also, such adjustment is cumbersome to operate. Further, defective operation of the tacker can occur if the user after making such an adjustment does not carefully secure the adjustable part of the tacker that determines the depth of penetration of the fastening elements.